Decoding method, encoding method, bitstream, decoder, encoder and storage medium

An encoding method, performed by an encoder, comprising:

• determining a reconstructed base mesh of a current image according to an original mesh of the current image;
• determining a subdivided mesh corresponding to the reconstructed base mesh and determining a value of first syntax identification information;
• when the value of the first syntax identification information represents single component displacement coding, determining displacement coefficients corresponding to a dimension of a specific vector by fitting the original mesh and the subdivided mesh in the dimension of the specific vector, wherein the specific vector comprises one of a normal vector, a tangent vector, and a bitangent vector;
• and
• encoding the displacement coefficients to obtain encoded bits and writing the encoded bits into a bitstream.

A decoder, comprising:

• a processor;
• and
• a memory for storing a computer program executable for the processor;
• wherein the processor is configured to:
• parse a bitstream to determine a reconstructed base mesh of a current image, displacement coefficients and a value of first syntax identification information, wherein the reconstructed base mesh is reconstructed based on an original mesh of the current image;
• determine a subdivided mesh according to the base mesh;
• and
• apply the displacement coefficients to subdivision points in the subdivided mesh in a dimension of a specific vector to obtain a reconstructed mesh when the value of the first syntax identification information represents single component displacement coding, wherein
• the specific vector comprises one of a normal vector, a tangent vector, and a bitangent vector, and the displacement coefficients are determined in the dimension of the specific vector by fitting the original mesh of the current image and the subdivided mesh in the dimension of the specific vector.